Safe Testing for Large-Scale Experimentation Platforms

In the past two decades, AB testing has proliferated to optimise products in digital domains. Traditional AB tests use fixed-horizon testing, determining the sample size of the experiment and continuing until the experiment has concluded. However, due to the feedback provided by modern data infrastructure, experimenters may take incorrect decisions based on preliminary results of the test. For this reason, anytime-valid inference (AVI) is seeing increased adoption as the modern experimenters method for rapid decision making in the world of data streaming. This work focuses on Safe Testing, a novel framework for experimentation that enables continuous analysis without elevating the risk of incorrect conclusions. There exist safe testing equivalents of many common statistical tests, including the z-test, the t-test, and the proportion test. We compare the efficacy of safe tests against classical tests and another method for AVI, the mixture sequential probability ratio test (mSPRT). Comparisons are conducted first on simulation and then by real-world data from a large technology company, Vinted, a large European online marketplace for second-hand clothing. Our findings indicate that safe tests require fewer samples to detect significant effects, encouraging its potential for broader adoption.Comment: 36 pages, 15 figure

Sit Back, Relax, And Tell Me All Your Secrets

The goal of this research is to describe an active learning opportunity that was conducted as a community service offering through our Center for Cybersecurity Education and Applied Research (CCEAR). As a secondary goal, the participants sought to gain real world experience by applying techniques and concepts studied in security classes. A local insurance company tasked the CCEAR with assembling a team of students to conduct penetration testing (including social engineering exploits) against company personnel. The endeavor allowed the insurance company to obtain information that would assess the effectiveness of employee training with regard to preventing the divulgence of sensitive information. The team of students assembled organized, planned and executed all penetration testing. This academic opportunity allowed the students to build experience transacting the social engineering while laying the groundwork for future projects that will allow additional students to build and expand the process outlined in this study

A Barren Landscape?

We consider the generation of a non-perturbative superpotential in F-theory compactifications with flux. We derive a necessary condition for the generation of such a superpotential in F-theory. For models with a single volume modulus, we show that the volume modulus is never stabilized by either abelian instantons or gaugino condensation. We then comment on how our analysis extends to a larger class of compactifications. From our results, it appears that among large volume string compactifications, metastable de Sitter vacua (should any exist) are non-generic.Comment: 14 pages, comments adde

Mixed-method approaches to strengthen economic evaluations in implementation research

Abstract Background Guidance from economic evaluations on which implementation strategies represent the best return on investment will be critical to advancing the Triple Aim of health care: improving patient care and population health while minimizing per-capita cost. The results of traditional (quantitative) economic evaluations are limited by a remaining “qualitative residual” of contextual information and stakeholders perspectives, which cannot be captured by monetary values alone and is particularly prevalent in implementation science research. The emergence of qualitative methods for economic evaluation offers a promising solution. Main body To maximize the contributions of economic evaluations to implementation science, we recommend that researchers embrace a mixed-methods research agenda that merges traditional quantitative approaches with innovative, contextually grounded qualitative methods. Such studies are exceedingly rare at present. To assist implementation scientists in making use of mixed methods in this research context, we present an adapted taxonomy of mixed-method studies relevant to economic evaluation. We then illustrate the application of mixed methods in a recently completed cost-effectiveness evaluation, making use of an adapted version of reporting standards for economic evaluations. Conclusions By incorporating qualitative methods, implementation researchers can enrich their economic evaluations with detailed, context-specific information that tells the full story of the costs and impacts of implementation. We end by providing suggestions for building a research agenda in mixed-method economic evaluation, along with more resources and training to support investigators who wish to answer our call to action.https://deepblue.lib.umich.edu/bitstream/2027.42/146781/1/13012_2018_Article_850.pd

Pathogenesis of Abdominal Aortic Aneurysm

Abdominal aortic aneurysms (AAAs) are encountered by many healthcare providers such as interventional radiologists, vascular surgeons, cardiologists, and general practitioners. Much effort has been placed in the screening, diagnosis, and treatment of AAA with somewhat little understanding of its pathophysiology. AAA is a complex disease typically segmented into a process of proteolysis, inflammation, and vascular smooth muscle cell (VSMC) apoptosis with oxidative stress balancing its components. AAA and other aortic syndromes such as aortic dissection share this same process. On the other hand, AAA formation and aortic pathology may be acquired through infection like in mycotic aneurysm or may be genetic in origin such as seen with Ehlers-Danlos and Marfan syndromes

Ammonia-methane combustion in tangential swirl burners for gas turbine power generation

Ammonia has been proposed as a potential energy storage medium in the transition towards a low-carbon economy. This paper details experimental results and numerical calculations obtained to progress towards optimisation of fuel injection and fluidic stabilisation in swirl burners with ammonia as the primary fuel. A generic tangential swirl burner has been employed to determine flame stability and emissions produced at different equivalence ratios using ammonia–methane blends. Experiments were performed under atmospheric and medium pressurised conditions using gas analysis and chemiluminescence to quantify emission concentrations and OH production zones respectively. Numerical calculations using GASEQ and CHEMKIN-PRO were performed to complement, compare with and extend experimental findings, hence improving understanding concerning the evolution of species when fuelling on ammonia blends. It is concluded that a fully premixed injection strategy is not appropriate for optimised ammonia combustion and that high flame instabilities can be produced at medium swirl numbers, hence necessitating lower swirl and a different injection strategy for optimised power generation utilising ammonia fuel blends

Lessons from building an automated pre-departure sequencer for airports

Commercial airports are under increasing pressure to comply with the Eurocontrol collaborative decision making (CDM) initiative, to ensure that information is passed between stakeholders, integrate automated decision support or make predictions. These systems can also aid effective operations beyond the airport by communicating scheduling decisions to other relevant parties, such as Eurocontrol, for passing on to downstream airports and enabling overall airspace improvements. One of the major CDM components is aimed at producing the target take-off times and target startup-approval times, i.e. scheduling when the aircraft should push back from the gates and start their engines and when they will take off. For medium-sized airports, a common choice for this is a “pre-departure sequencer” (PDS). In this paper, we describe the design and requirements challenges which arose during our development of a PDS system for medium sized international airports. Firstly, the scheduling problem is highly dynamic and event driven. Secondly, it is important to end-users that the system be predictable and, as far as possible, transparent in its operation, with decisions that can be explained. Thirdly, users can override decisions, and this information has to be taken into account. Finally, it is important that the system is as fair as possible for all users of the airport, and the interpretation of this is considered here. Together, these factors have influenced the design of the PDS system which has been built to work within an existing large system which is being used at many airport